1. Field of the Invention
The present invention relates to an antiallergic agent containing a benzopyran derivative or physiologically acceptable salts thereof as the active ingredient, and a benzopyran derivative which is useful as an antiallergic agent.
2. Description of Related Art
PCT International Publication No. WO92/13852 (U.S. Pat. No. 5,428,059) discloses that a benzopyran derivative represented by the general formula (III): 
wherein R1 is an alkyl group having 1-10 carbon atoms or an alkenyl group having 2-10 carbon atoms, and one of R2, R3, R4, and R5 is an alkoxy group and the others are hydrogen atoms,
and physiologically acceptable salts thereof are compounds which are useful as antiallergic agents, also have low toxicity, and are highly safe.
Also, Japanese Unexamined Patent Application, First Publication No. Hei 7-145189 (U.S. Pat. No. 5,525,595) discloses a benzopyran derivative wherein a glycosyl group is introduced into the 3-position of benzopyran. Japanese Unexamined Patent Application, First Publication No. Hei 7-145190 (U.S. Pat. No. 5,525,595) discloses a benzopyran derivative wherein a glycosyl group is introduced into the 4-position of benzopyran. Japanese Unexamined Patent Application, First Publication No. Hei 8-198890 (U.S. Pat. No. 5,580,552) discloses a benzopyran derivative wherein a glycosyl group is introduced into the 7-position of benzopyran. The benzopyran derivatives and physiologically acceptable salts thereof are compounds which are useful as antiallergic agents, also have markedly low toxicity, and are highly safe.
Compounds have hitherto been required which have a stronger antiallergic action, particularly an action of inhibiting both immediate and delayed type allergic reactions while maintaining the safeness of these benzopyran derivatives in terms of toxicity.
Japanese Unexamined Patent Application, First Publication No. Hei 9-315967 (U.S. Pat. No. 5,981,495) discloses, as a benzopyran derivative other than those described above, a benzopyran derivative represented by the general formula (IV): 
wherein R1 is an alkyl group having 1-10 carbon atoms or an alkenyl group having 2-10 carbon atoms, and R4 is an alkoxy group having 1-4 carbon atoms substituted with a hydroxy group.
This benzopyran derivative is useful as a treatment for heart disease. However, it was not known that the compound described in this publication has an excellent antiallergic action.
In Donald T. Witiak et al., J. Med. Chem., Vol. 31, p. 1437-1445, 1988, and U.S. Pat. No. 4,845,121, a benzopyran derivative represented by the general formula (V): 
wherein R3 and R4 are hydrogen atoms, halogen atoms, hydroxy groups, and alkyl groups having 1 to 6 carbon atoms, with the exception that both R3 and R4 are hydrogen atoms,
is disclosed as being useful as an antithrombotic agent. However, it was not known that the compounds described in these publications are effective in treating both immediate and delayed type allergies and are also markedly useful as drugs with fewer side effects.
An object to be achieved by the present invention is to provide a compound which is highly safe in terms of toxicity and has a stronger antiallergic action, and particularly has an action of inhibiting both immediate and delayed type allergic reactions.
To achieve the above object, the present invention provides an antiallergic agent including a benzopyran derivative represented by the general formula (I): 
wherein R1 is an alkyl group having 1-10 carbon atoms or an alkenyl group having 2-10 carbon atoms, and one of R2, R3, R4, and R5 is an alkoxy group substituted with a hydroxy group or an alkoxy group substituted with a carboxy group, and the others are hydrogen atoms,
or physiologically acceptable salts thereof as the active ingredient.
In addition, to achieve the above object, the present invention provides a benzopyran derivative represented by the general formula (II): 
wherein R1 is an alkyl group having 1-10 carbon atoms or an alkenyl group having 2-10 carbon atoms, and one of R2, R3, R4, and R5 is an alkoxy group substituted with a carboxy group, and the others are hydrogen atoms.
The antiallergic agent including the benzopyran derivative represented by the general formula (I) or physiologically acceptable salts thereof as the active ingredient of the present invention is highly safe in terms of toxicity, and has an antiallergic action which is stronger than that of various benzopyran derivatives as reported previously by the present inventors. It also exerts an excellent effect against both immediate and delayed type allergic diseases such as asthma.
Also, the benzopyran derivative represented by the general formula (II) of the present invention is highly safe in terms of toxicity, and is useful as a drug, particularly as an antiallergic agent.